Downey gives 'Thunder' its flash

As he already showed at the top of the summer movie season, flying high as superhero Tony Stark in "Iron Man," Downey can take an OK blockbuster and turn it into a must-see. He does it once again in "Tropic Thunder" in a performance that could have gone so wrong. Instead, it's perhaps the most brilliantly insane performance I've seen all year.

You can say Downey had no choice but to go all-out in his role of Kirk Lazarus, an Australian and intensely Method actor who slaps on some new skin pigment to play African-American sergeant Lincoln Osiris in a Vietnam War epic. But the joke is on acclaim-seeking cats like Russell Crowe more than on the black community.

As I said, it's a performance that could have so turned sour if the slightest hint of racist stereotyping revealed itself. (If he had pulled out a two-piece from Popeye's in the middle of a scene, this would be a completely different review.)

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But Downey plays the role with equal parts ridiculousness and reverence. His Lazarus is so intent on living inside the skin of a black man (he talks in character even when the cameras aren't rolling), he doesn't realize how much of an empty, personality-free void he is. He may be playing a black man, but he's really a black hole. Plus, there's an actual black actor, energy drink hawking rapper Alpa Chino (Brandon T. Jackson), around to remind him that he's still "Crackadile Dundee" under all that counterfeit color.

Downey's performance is the most continuously rewarding joke in "Thunder," a cartoonishly broad satire on Hollywood excess. Downey's Lazarus shares the bill on this flick with action star Tugg Speedman (director Ben Stiller) and funnyman Jeff Portnoy (Jack Black). They literally end up in the thick of it when their fed-up director (Steve Coogan) gets the idea to literally go guerrilla, dumping the cast in the jungle and filming the whole thing using hidden cameras.

Unfortunately, they get way off-track, heading into enemy territory for real.

Although Downey's character spends the bulk of the movie pretending to be somebody else, he is ironically the only A-lister with some grasp on reality.

Speedman, desperately seeking respectability as a serious actor, thinks all the gunshots fired at them are blanks, while drug addict Portnoy goes on a withdrawal tear, and Lazarus, along with Chino and young actor Kevin Sandusky (Jay Baruchel), is intent on getting out of this real/fake jungle alive.

As a comedy, "Thunder" is all over the place, occasionally hitting its mark. Needless to say, this is usually whenever Downey appears. Stiller, who wrote the film with Etan Cohen and actor Justin Theroux, is clearly mocking the same movie star pomposity he seems ashamed to be associated with. He even has Tom Cruise show up as a bald, pudgy studio head whose foul-mouthed tirades will surprise those who didn't see Cruise do it skinnier and with hair in "Magnolia."

But I have a feeling Cruise is there only to grind his ax. When his character turns down a ransom offer from a heroin cartel that captures Speedman, declaring that the kid is better off dead since he isn't the bankable star he once was, you can't help but think this is Cruise getting back at Paramount for letting him go a couple of years ago.

Nevertheless, Cruise still manages to drop a couple of guffaw-heavy scenes dancing to hip-hop. Stiller also has Matthew McConaughey appear as Speedman's fiercely loyal agent.

You don't have to have a subscription to Entertainment Weekly to get the inside-baseball in-jokes of "Thunder." Stiller plasters the movie with enough chaotic, rudimentary nuttiness (more so in the second half than in the looking-for-a-joke-that-works first) for those blissfully ignorant of Hollywood and its discontents (oh, how I envy you people!) to enjoy.

Downey is the one whose performance is truly a joy to behold. He's an oddball actor who upstages his two more bankable co-stars, in a movie about an oddball actor who upstages his two more bankable co-stars. The movie may be called "Tropic Thunder," but it's Downey who ends up bringing the most noise.